The present invention is related to a dielectric filter comprised of ceramic material, and particularly to the dielectric filter to which radio frequency signals (hereafter referred to as RF signals) having a frequency range from the ultra high frequency (UHF) bands to the relatively low frequency microwave bands can be coupled, and which is well adapted for a bandpass filter coupling the RF signals having a frequency range either from 825 mHz to 845 mHz or from 870 mHz to 890 mHz.
A conventional dielectric filter structure is described in detail in U.S. Pat. Nos. 4,386,328 and 4,283,697 assigned to the assignee of the present invention.
The conventional dielectric filter as described above is generally sited in a conductive closed housing so as to sufficiently apply ground to the filter and prevent radiation generated by the filter from leaking and causing an electrical influence on other electrical parts.
The conductive closed housing comprised of a main body and a lid is, further, constructed as a gastight casing by means of being soldered between the main body and the lid in a thermostatic and humidistatic atmosphere, and as a result, is gastight so that the filter is prevented from deteriorating a characteristic thereof due to humidity.
The above mentioned filter, therefore, requires many manufacturing process steps, and will be consequently expensive.